1. Field of the Invention
This invention relates to a cordless electric iron.
2. Description of the Prior Art
U.S. Pat. Nos. 2,714,650 and 3,760,149 disclose cordless electric irons in which iron bodies can be horizontally supported on stands.
U.S. Pat. No. 2,820,877 and Japanese published patent application 59-232597 disclose cordless irons in which iron bodies can be obliquely supported on stands.
U.S. Pat. Nos. 3,398,260 and 4,650,268 disclose cordless irons in which iron bodies can be placed on stands in a self-supporting manner.
In each of these prior art cordless irons, the iron body has a heater circuit and power feed terminals electrically connected to the heater circuit. The stand has electrodes which can be connected to the power feed terminals of the iron body. An electric cord leads from the electrodes of the stand. When the iron body is placed on the stand, the heater circuit is activated so that a sole plate of the iron body is heated. When the iron is used, the iron body is detached from the stand and the heater circuit is deactivated. Thus, during the use of the iron, the temperature of the sole plate of the iron body gradually drops. To prevent a considerable drop in the temperature of the sole plate of the iron body, it is necessary to frequently place the iron body back on the stand.
Japanese published unexamined patent application 64-52500 discloses an advanced cordless iron including a warning device and also a memory for storing a characteristic of an estimated drop in a temperature of the sole plate of the iron body which occurs during the use of the iron. At the moment of the detachment of the iron body from a stand, the temperature of the sole plate of the iron body is detected. This detected temperature and the estimated temperature drop characteristic are used to determine a reference time corresponding to a moment at which the temperature of the sole plate of the iron body drops to an unacceptable level. During the use of the iron, when the reference time elapses, the warning device is activated.
The cordless iron of Japanese patent application 64-52500 has the following problem. During the use of the iron, an actual drop in the temperature of the sole plate of the iron body depends on thermal conditions such as the heat capacity or the specific heat of a cloth pressed by the iron. Since the estimated temperature drop characteristic is predetermined for typical clothes, the warning process tends to be unreliable when the iron acts on clothes much different from the typical clothes in thermal conditions.